In time, the ancient Greek word delta took on a second meaning: a triangle or something triangle shaped, whether in geometry, carpentry, land survey, or other pursuits. By the mid-400s B.C. the Greeks were using this word to describe northern Egypt’s region of fertile alluvium, formed by the Nile River’s outlets diverging toward the Mediterranean Sea. On a modern map, the Nile Delta appears as a solid triangle, tip pointing southward.